Measuring instruments are indispensable for monitoring in physical or chemical processes, for instance, to ensure safe and smooth course of such processes.
Measuring instruments are employed in simple processes such as a domestic heating system but also in very complicated large-scale industrial plants.
Primarily in the latter permanent monitoring of parameters of a process is of salient importance. In a complex process a large number of measuring instruments may be required because of the numerous parameters to be monitored. Since it is difficult to carry out a permanent manual reading of many different measuring instruments, it is known to convert metered values into signals and transmit them through wires to a monitoring means.
Each measuring instrument is provided with a converting means for converting the respective metered values into electric signals, for instance. Furthermore, between each measuring instrument and the monitoring means a wire is provided for the transmission of the values. Frequently, specific plug elements are provided at the measuring instruments.
In the case of possible malfunctions or troubles it is also reasonable, however, to allow values to be read from the measuring instrument itself.
However, providing wires and/or plug-in elements at each of the measuring instruments is difficult and expensive.
Furthermore it is known that data can be transmitted via an antenna to appropriate receiving means, for instance via radio signal. For this purpose, appropriate transmitters are provided, for example.
It is a drawback of providing transmitters in a monitoring system that additional costs are incurred, more space is required and those devices and the antennas attached to them can be easily damaged or can be an obstacle, such as, for example, in the case of maintenance work.